1. Field of the Invention
This invention relates to a reader-printer for projecting the images of a microfilm onto a screen and a photosensitive surface.
2. Related Background Art
The image density of images photographically recorded in the frames of a microfilm is irregular in light and shade between the individual frame images. So, a reader-printer is provided with manually operated image density adjusting means such as a knob or a dial so that the density of the image of an output print can be adjusted to the desired light and shade in conformity with the image density of the desired frame image of the film to be printed. That is, by moving the knob or the like, image formation executing condition values such as the amount of image exposure and the development bias value of a printing mechanism relative to a photosensitive member are changed in conformity with the amount of movement of the knob or the like and a print of desired image density is output.
Recent years have seen the advent of a reader-printer of the print image density automatic adjustment type in which the density of a desired frame image to be printed is automatically detected and the image formation executing condition values of the printing mechanism are automatically changed to proper values in conformity with the detected density in order to save the time required for the above-described manual print image density adjustment.
The detection of the density of the image to be printed is divided into the following two types:
(1) detection is effected in the reader system optical path before the image scanning for printing is started; and PA1 (2) detection is effected with pre-scanning being done.
However, the type (1) above suffers from a disadvantage that if a density detecting sensor is disposed on the screen of the reader system, its shadow is created and the image breaks off.
The type (2) above suffers from a disadvantage that the step of pre-scanning the image surface of the film by a sensor is required before actually printing is started after the print button has been depressed and therefore, the first copying speed (the output time of the first print) is reduced.